If the intensity level at distance d of one trombone is 70 dB,what is the intensity level of 76 identical trombones,all at distance d?
A) 146 dB
B) 89 dB
C) 5320 dB
D) 76 dB
E) 82 dB

Question

Quizplus · Accepted Answer

Doubling the number of sound sources increases the intensity level by about 3 dB. Since 76 is 2^6 (or 64) times one trombone, the increase is approximately 6 times 3 dB = 18 dB. Adding this to the original 70 dB gives 88 dB, but since 76 is slightly more than 64, the correct answer is a bit more, making 89 dB the best choice.

If the Intensity Level at Distance D of One Trombone